1. Field of the Invention
The present invention relates to a motorized window treatment, and more particularly, to a self-contained tensioned roller shade system that allows for easy installation into a window opening oriented, for example, in a non-vertical plane, such as a skylight.
2. Description of the Related Art
Typical motorized window treatments, such as, for example, roller shades, draperies, roman shades, and venetian blinds, are mounted in front of vertically-oriented windows to prevent sunlight from entering a space and to provide privacy. A motorized roller shade includes a flexible shade fabric wound onto an elongated roller tube. The flexible shade fabric typically includes a weighted hembar at a lower end of the shade fabric, such that the shade fabric is pulled down by gravity and simply hangs in front of the window. Motorized roller shades include a drive system engaging the roller tube to provide for tube rotation, such that the lower end of the shade fabric can be raised and lowered by rotating the roller tube.
While most windows are oriented vertically, skylight windows are typically mounted in a non-vertical plane. Some prior art motorized roller shade systems have been installed in skylight windows. These prior art skylight shade systems typically comprise tensioning systems, in which an amount of tension is provided to the shade fabric to minimize the sagging in the shade fabric. One prior art tensioning system includes two roller tubes where each roller tube is rotated by a separate motor. Specifically, one of the roller tubes is coupled to a first end of the shade fabric and windingly receives the shade fabric. The second roller tube winds up cables that are attached to a second end of the shade fabric, such that the shade fabric may be pulled by the cables as the second roller tube rotates. Since the motor in each of the roller tubes is stressed by the tension of the shade fabric, the motors must be larger (and thus noisier) than typical motors. Further, separately controlling each of the motors of this “dual-motor” shade system (e.g., to pull the shade fabric, to stop movement of the shade fabric, to apply the appropriate tension to the shade fabric) is rather complex and unreliable.
Another prior art tensioning system also includes two roller tubes with a first roller tube rotated by a motor (at a first end of the shade fabric) and a second roller tube that is spring-biased to provide tension in the shade fabric. Once again, the motor is stressed by the tension of the shade fabric and thus is larger and noisier than a typical motor. Further, the spring of the spring-biased roller tube limits the size (i.e., the length) of the shade fabric that may be tensioned by the roller shade system. An example of such a tensioning system is described in greater detail in U.S. Pat. No. 5,467,266, issued Nov. 14, 1995, entitled MOTOR-OPERATED WINDOW COVER. Both of these prior art tensioning systems require all of the system components to be individually installed in the opening, which can be rather difficult for a skylight window.
There is a need for a skylight shade system that minimizes the stress on the motor due to the tension in the shade fabric. Further, there is also a need for a skylight shade system that is easy to install and is scalable to allow for multiple sizes of roller tubes and shade fabrics.